Catalyst for preparing unsaturated acids and aldehydes

ABSTRACT

A CATALYST CONTAINING MOLYBDENUM OXIDE, TELLURIUM OXIDE AND THROIUM PHOSPHATE IS DISCLOSED FOR THE SIMULTANEOUS PREPARATION OF UNSATURATED ALDEHYDES AND UNSATURATED ACIDS BY REACTING A MONOOLEFIN WITH OXYGEN.

United States Patent O Int. c1. B013 11/82 U.S. Cl. 252-437 2 Claims ABSTRACT OF THE DISCLOSURE A catalyst containing molybdenum oxide, tellurium oxide and thorium phosphate is disclosed for the simultaneous preparation of unsaturated aldehydes and unsaturated acids by reacting a monoolefin with oxygen.

This is a division of application Ser. No. 619,190 filed Feb. 28, 1967, and now Pat. No. 3,520,923.

BACKGROUND OF THE INVENTION Many of the catalysts and procedures for oxidizing monoolefinic gaseous hydrocarbons to monoolefinically unsaturated aldehydes or monoolefinically unsaturated carboxylic acids with the same number of carbon atoms as the hydrocarbon have certain deficiencies. The catalysts either have a short active life; they convert only a portion of the hydrocarbon to desired end groups per pass; they oxidize the hydrocarbon excessively to form high proportions of carbon monoxide or carbon dioxide or both; they are not sufficiently selective, so that the hydrocarbon molecule is attacked at both the olefinic unsaturation and at a methyl group; or the oxidation of the olefin either does not proceed beyond the aldehyde stage or goes all the way to the acid.

SUMMARY OF THE INVENTION This invention relates to catalysts comprising a mixture of a molybdenum, tellurium, oxygen, thorium and phosphorous in a molar ratio, calculated as, 100 M 100 TeO and 10-100 of a thorium phosphate, and to a method of preparing acrolein and acrylic acid, or methacrolein and methacrylic acid by passing vapors of propylene or isobutylene and an oxygen containing gas over the catalyst at a temperature of from about 300 C. to about 550 C. The catalyst can also be designated as MO TE 1oTh2 2 P2 O o With the P being in the form of a phosphate, i.e., each P is attached to 3 or 4 oxygen atoms and the ratio of Th to P is from 1:2 to 3:4.

The catalysts of this invention have long life and will convert a substantial amount, more than 50% per pass, of a gaseous monoolefin such as propylene or isobutylene to yield high proportions of both acrolein and acrylic acid, or methacrolein and methacrylic acid. The catalyst also produces a wide ratio of olefinic aldehyde to monoolefinically unsaturated carboxylic acid by controlling reaction conditions or catalyst composition. Molpercent efficiencies as high as about 40 for the aldehyde and about 50 for the unsaturated carboxylic acid have been obtained with the catalyst and process of this invention. Usually when the efficiency for conversion of 3,585,152 Patented June 15, 1971 DETAILED DESCRIPTION The reactants The essential reactants are 1) propylene or isobutylene and (2) an oxygen-containing gas, which can be pure oxygen, oxygen diluted with an inert gas, oxygen enriched air or air without additional oxygen. For reasons of economy, air is the preferred oxygen-containing reactant.

For the purpose of this invention the hydrocarbons which are oxidized can be defined generically by the formula H (OH2)01 CHa( 3 -OH2 The end products formed result from the oxidation of only one methyl group on the hydrocarbon molecule while the teerminal CH =C remains intact.

Stoichiometric ratios of oxygen to olefin for the purpose of this invention are 1.5 to 4 to 1. Slightly lower amounts of oxygen can be used at a sacrifice of yield. It is preferred to use 33 to 66% excess oxygen. Larger excesses do not impair the yields of aldehydes and acids, but for practical considerations an excess much above would require extremely large equipment for a given production capacity, particularly if air is used.

The addition of steam into the reactor along with the hydrocarbon and oxygen-containing gas is desirable but not absolutely essential. The function of steam is not clear, but it seems to reduce the amount of carbon monoxide and dioxide in the effluent gases. Other diluent gases can be used. Saturated hydrocarbons such as propane are rather inert under the reaction conditions. Nitrogen, argon, krypton or other known inert gases can be used as diluents if desired but are not preferred because of the added cost.

The catalyst and its preparation There are several methods for the preparation of the catalyst, which can be supported or unsupported. It is possible to dissolve each of the starting ingredients in water and combine them from the aqueous solutions or the ingredients can be dry blended. Because of the more uniform blend obtained by the solution procedure, it is preferred.

A general procedure for preparing a catalyst from water soluble ingredients is to (1) dissolve the requisite amount of a molybdenum salt, a tellurium salt and a thorium salt in water (2) add the requisite amount of phosphoric acid to the thorium salt solution, (3) add the tellurium salt solution to the molybdenum salt solution, and (4) then add the thorium salt-phosphoric acid mixture to the molybdenum-tellurium salt mixture. The catalyst is then dried and baked at 400 C. for about 16 hours.

Supported catalysts can be prepared by adding a dry support or an aqueous slurry thereof to the aqueous solution of catalyst or the aqueous catalyst ingredients can be added to the slurry of the support. Alternatively a slurry of the catalyst ingredients can be prepared in water, then dried an baked. For supported catalysts the aqueous slurry" of the catalyst ingredients can be added to an aqueous supsension of the support or vice versa, and then dried and baked. Another method is to blend the dry ingredients of the desired particle size and then mix them thoroughly. Thorough blending and uniform particle size is desired.

A specific example (A) of the solution method is as follows.

(1) Dissolve 158.94 g. of (NH 6MO7O24'4H2O in 450 ml. of water.

(2) Dissolve 47.88 g. of Te in 100 ml. cone. HCl and add to (1).

(3) Dissolve 165.67 g. of Th(NO -4H O in water and add 69.2 g. of 85% H PO Add this mixture slowly to the mixture of (l) and (2) Dry on a steam bath and calcine in a hot tube oven for 16 hours at 400 C. Thereafter, the catalyst is ground to the desired mesh size and sieved.

An example (B) of preparations of a supported catalyst (1) Dissolve 79.47 g. of (NH4)6MO7O24'4H2O in 300 mil. of water and add to 90 grams of catalyst silica in 200 ml. of water. (Microspheroidal silica Ludox HS.)

(2) Dissolve 23.94 g. of TeO in 50 ml. of concentrated avoid an explosive mixture, the limiting of air aids in that direction.

The mol ratio of steam to propylene or isobutylene can range from O to about 5 to 7, but best results are obtained with molar ratios of about 3 to 5 per mol of olefin and for this reason are preferred.

The contact time can vary considerably in the range of about 2 to 70 seconds calculated at 25 C. and 760 mm. Best results are obtained in a range of about 8 to 54 seconds and this range is preferred. Longer contact times usually favor the production of acid at any given temperature.

The particle size of catalyst for fixed bed operations used is from 10-18 mesh, passes 10 mesh, held on 18 HQ d i ith (1), (US). As is known, for fixed beds, the size may be a (3) Dissolve 82.83 g. of Th(NO -4H O in 200 m1, wide range of particle sizes. For fluid bed systems, a useof water and add 34.6 g. of 85% H PO This mixture ful catalyst size is to pass 80 and be held on 325 mesh was added slowly to the mixture of (1) and (2). Dry on a steam bath and bake in a hot tube for 16 hours at 400 C. The reaction can be run at atmospheric pressure, in a Thereafter, the catalyst is ground to the desired mesh size 20 Partial Vacuum under induced Pressure P to 50400 for fix d or fluid b d a ti d i d, p.s.i. Atmospheric pressure is preferred for fixed bed sys- Among the suitable supports are silica, silica containtoms and a Pressure of 1 to 100 P- for fluid bod ing i l h as diatomaceous h, kigselguhf actions. Operation at a pressure which is below the dew silicon carbide, clay, aluminum oxides and even carbon, point of the unsaturated acid at the reaction temperature although the latter tends to be consumed during the re- 20 is advantageousaction. The data in the examples show that wide variations in Such catalysts, with molar ratios of 100 MO, 10400 percentages of unsaturated acids and aldehydes can be TC and 10400 of a thorium Phosphate can be used for obtalned w1th a slngle catalyst, using fixed ratio of reoxidizing the monoolefinic hydrocarbon to aldehyde aFtants but g g h temPerature and/or Fontact and/or carboxylic acid. The catalyst contains chemically time Fulther Yananon ls.obt.amabl? by controlhng the bound oxygen so that the generic formula can be written p rfaactlon the catalyst Moos1001-6021odoornlpzo,7 or other thorium phos pos1t1onsw1th1nthel1m1ts set forth here1n. p ate The phosphate can be a P0 radical, a rophosphate, or a polyphosphate. W EXAMPLES 1 5 Reaction conditions A series of runs were made in a fixed bed reactor of a high silica (Vycor) glass tube 12 inches long and 30 mm. Tb reaotlofl can be Carried out In either a X r outer diameter. The reactor had three inlets, one for air, fiuldlled o y 40 one for steam and one for propylene. Three external The reaotlon tompol'atufo can range from about electrically operated heating coils were wound on the to For the Oxidation of Propylene, the p reactor. One of the coils extended along the entire length forfod Tango 18 from about to about of the reactor and each of the remaining coils extended Below the Conversion P P is lowol" and low only about one half the length of the reactor. Outlet temperature tend? to Produce more aldohyde- Usually, vapors were passed through a short water cooled cona longer contact tlme 1s needed at lower temperatures to dchselg U d d gases were passed h h a gas obtain the yields of desired products obtainable at higher chromatograph (P ki -E1 d l 1541)) d l d temperatures- Above 4500 in the Propylbne Oxidation, continuously. The liquid condensate was weighed and then some of o desired l Products PPF to be Oxidized to analyzed for acrylic acid and acrolein in the gas chromacarbon ox1des. For 1sobutylene, ox1dation temperatures tograph The reactor was filled i 170 v 1 of uhsup. of 375-550 C. are desirable w1th the preferred range ported catalyst made b the solution method (A) being scribed above, using a ratio of 75 M00 25 TeO and 25 The molar ratio of oxygen to propylene or isobutylene ThP O Empirically the catalyst is MO75T25Tl125P50O45o should be at least 2 to 1 for good conversion and yields. and the P is present as P 0 The catalyst Was not sup- Sme excess oxygen, 33 to 66 mol percent is even more ported and had a mesh size of 10-18 (U.S. Sieve). Steam desirable and is preferred. There is no critical upper limit at a temperature of ZOO-250 C. was first passed into the as to the amount of oxygen, but when air is used as the reactor. Then propylene and air were separately fed into oxygen-containing gas it becomes apparent that too great the stream of water vapor. This mixture then passed an excess will require large reactors, pumps, compressors through a pre-heater and entered the reactor at about and other auxiliary equipment for any given amount of 200250 C. The reactor was pre-heated to about 285 C. desired end product. It is therefore best to limit the before the gas feed was begun. The ratio of reactants per amount of air to provide a 33 to 66% excess of oxygen. mol of propylene, contact time (STP), the reaction tem- This range provides the largest proportion of acid, under perature in C., and the data obtained in these runs is given reaction conditions. Also, since care is needed to summarized in the TableAbelow.

TABLE A Mol percent yield Mol on propylene M01 percent Contact percent converted efficiency Run Oxygen, Steam, Temp., time, propylene No. mols mols 0. seconds converted Aer. AA Aer. AA

NorE.-Aer.=Aero1ein: AA=Aerylie acid.

by use of rheostats, The reaction conditions, ratio of re actants and results are set forth in Table B.

TABLE B Mol percent yield Steam, Mel on propylene Mol percent Oxygen, mols/ Contact percent converted elficieney Run mols/ mol tlme, Temp, propylene No. mol H OaH seconds C. converted Aer. AA Aer. AA

NorE.Acr.=Acrolein; AA=Acrylic acid.

15 I claim:

EXAMPLES 6-9 A supported catalyst prepared according to procedure (B) above was prepared to the ratio MoO -25 T e0 25 ThP O -250 SiO The particle size was between and 325 mesh (U.S. Sieve), The runs were made in a fluidized bed. In these runs the reactor was a high silica glass cylinder with an CD. of 38 mm. and height of 12 inches. It was filled to a height about 4 inches ml.). In all cases the catalyst was fluidized by first injecting hot air into the reactor and then adding the requisite amounts of steam and propylene. The gases were preheated to about 250 C. prior to entering the reactor The reactor was heated externally with electrical resistance wire, and the reaction temperature was controlled UNITED STATES PATENTS 5/1969 Eden 252-437X 4/1970 Eden 252437 PATRICK P. GARUIN, Primary Examiner US. Cl. X.R. 260533N, 604 

